An inverter is a power converter that converts direct current (DC) into alternating current (AC). Traditionally, this has meant one, centrally-located inverter converting all of the DC current from the entire PV array into grid-compliant AC power. A Micro-inverter is a fully integrated device that converts the DC output of a single solar module into grid-compliant AC power. AC power then travels upstream through an ordinary branch circuit, and to the service panel. A Micro-inverter system, then, is a federation of multiple micro-inverters all along a branch circuit, and/or within multiple branch circuits, which are all converting DC to AC, all injecting their current upstream, and reporting back in real-time regarding their individual performance.

A few days ago, there was a thread asking about 250 Watt micro GT inverters that could be found on Ebay and the Enphase came up in discussion there.

While it may still be difficult to obtain quantities of retail units at this time--Enphase appears to be the first "real" micro inverter that is installed one per solar panel which are approved for use as Grid Tie / Utility Interactive Inverters in the US (and probably Canada).

While they are not "cheap" (at this time) for use in larger systems, they may fill specific needs for smaller systems or other requirements.

And, as a warning to others, there are several small (250 watt or so) Grid Tie Inverters available on other websites. Since the units (at least those websites I have visited) are not listed to UL/NRTL requirements, they are not legal to install and not safe either (either for the homeowner or electric utility workers). And in any case, no Grid Tied system can be connected to an electric utility mains without building permits and approval by the local utility.

Please feel free to discuss the Enphase product here, or in the other linked thread above.

Here's my opinion on ENPHASE micro-inverters. These,Gentleman are the game changer. I am basing my entire PV business on these inverters. I have done a number of estimates where I have speced only these.I've used them for one job. Good for residential and commercial. They are economical, easy to install, are mounted under the panels, are more efficient, no hassles as to where to locate PV equipment, and the best part of all AC output. No string calculations, no DC rated ANYTHING,no greenfield(flex), no conduit. Once it leaves the roof mounting rack system, it's all AC. You can put 14 of them on one string which uses a 2-pole 20 ampere breaker.I ran 10/3 MC cable through the dwelling, or would install conduit in commercial(depends on AHJ) to the utility required disconnect, then to the load center. No need for demand meter, if you sign on for the enpower monitoring,(which is $9US for 10 years for each inverter used) The uploads are made automatically. You can see if there is a panel or inverter producing less energy and change the panel/inverter if necessary. Do that with a big box inverter. No special cables to run for monitoring, it monitors from the AC outlet you plug the empower unit into. UL listed with GFC protection as required for residential rooftop installation. I am an electrician by trade, this makes transitioning my business to PV easier for my employees. I used the 175 models for the residential job(which happened to be my home) They have been discontinued and replaced with the 190 model. 175's are still available if you hunt for them. 190's are available in 240v and 208v for commercial & 3-phase applications. Trying to hoard the 175's. 190's will be hard to come by when they finally hit the retail market. Another Company venturing into micro-inverters is Helios(www.helios.com)

They certainly sound like a great advancement in easy solar installs, but for ALBANYSOLARGUY's sake I hope they don't all start to fail after a few years' weather exposure. Not everywhere has the same climate. In my experience the extremes of temp and humidity wreak havoc on electronic devices. The more of the system subjected to such conditions, the greater the likelihood for failure.

No different than mounting inverter equipment on the outside of a dwelling. Enphase modules are installed beneath the panels. Big box inverters exterior mounted could have the same problems mentioned by cariboocoot. The old guard not willing to try something new. I received the same reaction from other installers in my area.The enphase modules are more energy efficient, and maximize the generation of each panel. Not possible with a big box inverter out of the box. Don't knock them until you've installed them.

Your putting allot of faith into something that has virtually no field data over time. As for the efficiency claims and temperatures exposures, that's flat out wrong. A Xantrex GT5.0 or similar wattage Sunnyboy are higher efficiency and there not behind a panel on the roof that will exceed 65C. The Enpase specified efficiency are at much lower temperatures

You will be the one, at your expense that gets the calls when an inverter need to be replaced and you have to get into the middle on an array to swap out a panel when its the inverter the failed.

The "Old Guard" is more than willing to use improved technology, the enphase can't make a single factual claim to why its better. You have to do the exact same wiring on the roof for AC or DC , its will be lower efficiency due to the heat and harvest wise single string configurations can harvest the exact amount of energy that 20 little tracking inverts could do and they cost much more because you can't go with the best priced panels and a central inverter price per watt is close to 1/3 the cost of using enphase

Its good if you want to offer it to customers as an option, bad for you if they pick a competitor that would offer a field proven solution that your not willing to provide.

By economical, did you mean that getting, say, 14 Enphases is cheaper than one big inverter? I would welcome that, as it was trouble for me to lift my heavy inverter onto the mount. However, I'm also cheap, so if heaving the big inverter cost less, I would still do it.

The Enphase gives some people that option of starting small...
However, as Guppy says, these units are going to be much more prone to early failure just because they are out in the elements and subjected to HOT & COLD & HOT & COLD &......

A standard inverter can be mounted in the shade, the Enphase cannot. In addition, solar panels always run quite a bit hotter than the surrounding air - and the Enphase inverters will be very close to that same elevated temperature.

The Enphase gives some people that option of starting small...
However, as Guppy says, these units are going to be much more prone to early failure just because they are out in the elements and subjected to HOT & COLD & HOT & COLD &......

Still, the Enphase seems like a great unit, so far anyway.
boB

Sos havent got the quote thing quite sussed yet,

but boB Sylvester (ok he is not a real Cat) but he needs 2 know where your swinging on this cos my dog Hugo ( a real dog ) is baffled and hes a clever dog,,, he always turns up 4 chow : now were are both confused

OK, so each inverter needs its own wires.... AND, those wires are a bit larger for that run to the shade than the 240VAC wires...

But, still.... why can't you do that ?

boB

I think the question is: Why would you?
When you go to a higher wattage set-up, having one set of wires coming from multiple panels on the roof feeding one inverter just makes more sense than dozens of little panel/inverters each with its own wires coming down and tying into the house wiring, doesn't it? The more components to a system, the more things there are to fail.

I thought that maybe there was some legal reason that even only ONE Enphase couldn't be wired away from the module. I don't care about 20 of them. If I
was going to use 20 modules, I'd use a single inverter and an array most likely.
This Enphase is still a great way for people to enter into this technology at a low price.

When I'm told that something can't be done, I just like to know why. This is mainly because there seem to be lots of things that I'm not supposed to be able to do.... but, I'm doing them just the same.

I thought that maybe there was some legal reason that even only ONE Enphase couldn't be wired away from the module. I don't care about 20 of them. If I
was going to use 20 modules, I'd use a single inverter and an array most likely.
This Enphase is still a great way for people to enter into this technology at a low price.

When I'm told that something can't be done, I just like to know why. This is mainly because there seem to be lots of things that I'm not supposed to be able to do.... but, I'm doing them just the same.

boB

Aha! So what you are wondering is: can you take the Enphase inverter off its panel and mount it remotely in a cooler environment?

Good question. Anybody know the answer?
But then, how does that compare with buying a separate 200 W panel & GT inverter? I don't think there are any other GTI's that small out there. Not much point to GT with only 200 Watts, is there?

The big problem (from my earlier post) with removing the Enphase off of the panels is that you have lost the whole advantage of series connected high voltage DC reducing your wiring costs... (320 VDC vs 32 VDC operating panel voltage, Plosses=I^2_*_R -- so 10x the current means 100x the losses with same wire awg--You need 100x the amount of copper to ameliorate the losses from the lower Vmp panel string voltages).

To build a system with exactly the same efficiency, one would need to spend almost 100x as much on the copper wire for a "remote" mounted Enphase cluster vs a high voltage central inverter system...

I guess, if you where roof mounting--you could do a roof penetration under every panel or 4 and place the Enphase units under the roof in the attic... Would it be better? Less rain, perhaps less heat in the attic. However, you now have your roof even more peppered with potential points of leakage. And would I want to wire up 20 Enphase inverters + AC in my attic--not my first choice.

Of course, if you only need a few hundred watts of GT power--Enphase is the only game in town at this time.

The big problem (from my earlier post) with removing the Enphase off of the panels is that you have lost the whole advantage of series connected high voltage DC reducing your wiring costs... (320 VDC vs 32 VDC operating panel voltage, Plosses=I^2_*_R -- so 10x the current means 100x the losses with same wire awg--You need 100x the amount of copper to ameliorate the losses from the lower Vmp panel string voltages).
<< snip some >>
-Bill

Yep ! This is all so very true ! Of course, when that unit heats up behind the panel, it will get less efficient too. Not sure which is more lossy though, the wire or the hot unit. You'd just have to run larger diameter wire to make up for the loss... In this case, shade might be very close by and the wire might not be too long a wire run away. The whole idea behind wanting to put it in the shade has to do with inverter life. It's going to be a tough life for the inverter right behind the module. Isn't this an analogy to the SWWP Sky Stream inverter being mounted inside the nacel of the turbine ??? Lots of folks say that's a bad idea.... For different reasons of course.

These inverters do not come mounted to a panel so you can put them anywhere you like to, physically.

A very handy rule of thumb that comes out of engineering and materials physics is the rule of 2 for 10C (18 degrees F).

Basically, anything that increases temperature by 10C will experience a reduction in life by a factor of 2.

Raise the temperature from 35C to 65C--the life will go down by 1/2*1/2*1/2=1/8th of the life at the lower temperature.

Also, applies to the cooling side--you cool something by 10C (18F), the device will last 2x longer.

The other killer for electronics (and most materials) is temperature cycling... In the old days--I found that 2 weeks in a thermal cycling chamber fo disk drives, after cycling ~3 times per day (40F-120F-40F)--anything that lasted over two week was probably going to be a good disk drive.

Operating an inverter under solar panels on a roof, with extreme temperatures and thermal cycling will definitely show how well Enphase has designed/constructed their product.